UNIT 1 INTRODUCTION TO IRRIGATION ENGINEERING Structure 1.1 Introduction Objectives 1.2 Need for Irrigation 1.2.1 Growth of Population and Consequent Strategy 1.2.2 Historical Background 1.2.3 Planning of Irrigation Projects: Inputs 1.2.4 History of Development of Irrigation in India 1.3 Advantages and Disadvantages of Irrigation 1.3.1 Environmental Effects 1.3.2 Environmental Issues -Environmental Impact Assessment (EIA) 1.3.3 Sustainable Development 1.4 Summary 1.5 Key Words 1.6 Answers to SAQs 1.1 INTRODUCTION This unit seeks to introduce to you the complexities of irrigation project planning. Objectives After study@g this mlit you should be able to: know as to why irrigation is required, understand the meaning and importance of "Masterplan'; know the history of development of irrigation, understand the impact of irrigation on environment, and get aquainted with the concept of sustainable development. 1.2 NEED FOR IRRIGATION Food is one of the basic essentials to sustain life. But, growing food needs'water as an Input which is not always and everywhere available in required quantities. Therefore, iirtificial application of water to plants, namely irrigation hecomes necessary. 1.2.1 Growth of Population and Consequent'Strategy You may recall from your earlier studies that India is the extension of one of the oldest civilizations: India of today is at the cross roads due to the exploding population. Today, to sustain development and to progress further, it requires an Herculean effort. The result5 of 1992 census reveal that during the decade of the '80s the average annual growth in population has been 2.11%.Do yoa know that the rate of population growth is not uniform all over the country, and it varies from 4.50%in Nagaland to 1.31%in Kerala? In other words, in absolute terms we were 238 millions in 1901 (undivided India) and now we are 875 millions in 1992 (Table T.1). Table 1.1: Total Population of Indla (In millions) Year 1901 1961 1971 1981 1991 1997* Population 238 43 9 538 683 853 985 The density of population has risen from 216 persons per sq km in 1981 to 267 per sq km in 1991. As you can see in your daily life such a growth has led to the increasing soil - PW - Water pressure on the basic life support systems of land, water, atmosphere, flora, and fauna. R-Inw* DO you how that there is a need to support nearly 2056 of the world's farm animal population that lives in India, and also forests have been dwindling and hardly 23% of the geographic area consfitutes this component? In this context, imgation development has to take place with the following aims: i) Physical access to food, at economical price, for all people at all times -&led Food Security [FAO's resolution on Food Security Act, 1985 of the USA iS an example of legal framework for sustainable use of land and water], and ii) Access to balhced die6 and safe drinking water called Nutrition Security. L The future requirement for Indian irrigation is that we have to develop the limiJed wakr resources at a rate that :-mintaim a "sustainable development". This assumes equity, efficient economic systein, ecological harmony and a stable social system. Knowing that there are many interlinked facets of water resources development, the concept of conservation of land (erosion) and water, intense cultivation, recycling of waste water, and making of a better use of the already created potentials by employing modern water management methods, are to be linked appropriately. Also, experts favour reorientfag the development from macro-system to micro-system, and free surface flow system to pipe (pressure) system. There is basically a need to conserve water, and to increase irrigatib efficiency, and hence, the stress on "sustaining the development". IBox 1.1 What is Sustainable Development ? t It is the development that meets the need of the present without' compromising the life of the future generation. 1.2.2 Historical Background Records regarding use of irrigation extend back to 3000 B .C. India's early irrigation history ranks with that of Egypt and China; and especially in the past 100 years hdia ha& constructed some of the most magnificent irrigation works to be found in the world. Indian enterprises with the accompaying thoroughnev with which each detail is , elaborated, and the wonderful performance of all the irrigation structyres bas been highlighted by Wilson (1890). Yo may be aware that the modem development of irrigation has not'oIlly freed 1f;dh !I fro!I the scourge of fearful famines, but also has ushered in confidence and self sufficiency on the food front of the country. Table 1.2 :Food Pductlon Periud I' 'F%e Plan (1951) 52:O I Five Year Plan (195 1 - 1956) II Five Year Plan (1956 - 1961) EI mve Year Plan (196 1 - 1966) Annud Plans ( 1966 - 1969) IV Five Yea! Plan (1969 - 1974) V Five Year Plan (1974 - 1978) . Annual Plan (1978 - 1980) 131.0 1 VI Five Year Plan (1 983- 1985) 152.3 VII Five Year Plan (1985 - 1990) 152.0 1987 - 88 (drought year) 140.0 1988 - 89 169.9 ' 1989-90 170.63 1990-91 ' + a 1?7.q~j . I* 1991,- 92 . , 167.00 ,. , India has done well in most years and could have even exported foodgrdns. To achieve lnt~oductionto nutritional sufficiency, the real stumbling block is the fast rate of growth of population lrllg~tionEngineering which outpaces the increases in agricultural production (Table 1.2). This competitive race continues and India requires a carefully planned strategy for development within this scenario. The art of irrigation management has to be based on past experience and skills employed. For this purpose we must have recorded evidences of the past experiences of eminent engineers. Irrigation comprises a vast field of knowledge. It is a fascinating field since it provides service to the community composed of several individuals having different purposes, different aspirations, different attainments, varying status in life (engineers, agronomists, economists, sociologists, farmers, head enders, tail enders, farm labourers etc.). In short, it is a field which caters to a multitude of people from different cross-sections involving five different aspects, viz., planning, design, construction, management and administration. BOX1.2 a) What Is Irrigation? Irrigation is the application of water artificially to the soil for the purpose of food production. Thus, the water supplied supplements the water available from rainfall and other sources such as soil moisture. b) Why irrigation? The increase in demand for food requires large area to be brought under cultivation and going in for more intense growing. In other words, extensive and intensive aspects of development have to be addressed to. But, the required quantity of water at the appropriate time may not be usually available in nature; and rainwater is ill distributed both spatially and temporally. Hence, water is to be supplied according to the requirement of crops. , Complexlty of Irrigation Planning Irrigation projects are complex agricultural development enterprises which require the distribution of controlled quantities of water to suitable areas of land together with a large %umber of essential complementary inputs to Allow as well as increase crpp production. Successful irrigation planning, development and management include the establishment of firm objectives, direction of planning activities, operation and management of various components (Figure 1.1). IIrr~gut~onMethods 8 Flgum 1.1; A Schematic Magrun Depleting Orgmlsstlon, Opemtlon md Maintenance Asp& d Idgation Phnning Soil Plant Water - B0$1.3 , , Relatiomhip in Irdgatlon The number of villages in India is 507000 with a nualpopulation *. of 631.22 million as per 1991 census. The money invested in industrial development provides a higher direct ieturi~~than investments in irrigation (How and why?). Then why should we invest in irrigation'? The prime objectives of irrigation are to provide the basis for economic developil~ei~tand to eliminate hunger and poverty. Full realisation of the benefits from modem irrigation farming depends on the provision of a wide range of services. Year Percentage -- 1901 1947 1971 1981 1991 100 90 80 70 60 - 50 40 30 20 10 10 17.3 19.9 23.43 2 hC% 0 u u u U u U = Estimated uhnpopulation Figure 12: VPliaSion of Rural Population over Past 90 Years 'Experience has shown that industrial development does not take place until a nation can provide food, cloth, shelter and water to its pTople, these being the basic needs. Can you imagine that a high proportion of the nation's population lives in rural areas (Figure 1.2) and a major portion of the total national productive effDrt is spent 011 agriculture? Increased agricultural production, therefbre, means much to us, but achieving a substantial increase in agricultural production is not an easy task (Table 1.3). In terms of national gains, increased food production means: i) Insurance against drought and famine. ii) Saving of substantial amounts of scarce foreign exchange and avoidance of import of food. In other words it implies self sufficiency. iii) A higher level of nutrition for the entire population. iv) Exporting of food grains resulting in increased national income, which thereby generates confidence in people. Table 1.3: Projection of Future Food Requirement for Projected Population - - - Year Food Population (A. D.) (million tonne) (million) 2000 250 1000 2010 300 1200 2025 375 2050 460 Irrigation 1s an age old art, in fact as old as civilisauon itself. Adherence to tradition is lotrod~cti~nto prevalent due to high ~~alattachment. Thus, the introduction of new techniques in irrigation Engineering ' the methods of food production is a difficult proposition (Refer Box 1.4 for a contrasting picture).